| Slant Six Forum https://slantsix.org/forum/ |
|
| shaving head https://slantsix.org/forum/viewtopic.php?t=40916 |
Page 1 of 1 |
| Author: | userhelp [ Tue Jul 06, 2010 7:08 pm ] |
| Post subject: | shaving head |
My buddy and I are new to bracket racing. How many thousandths do we shave the head on a 225 slant to go from 8 1/4 to 9 1/4 comp. Will this interfere with the push rods and valve clearance? Also what is the max that can be shaved and not interfere with the push rods and valve clearance. Thanks. |
|
| Author: | Joshie225 [ Tue Jul 06, 2010 7:38 pm ] |
| Post subject: | |
I'll bet you $1 you're under 8.25:1. To go from 8.25:1 to 9.25:1 requires a combustion chamber volume reduction of 10.25cc. This is about .068" off the head, but if you're using a thicker composition head gasket you'll have to find the thickness difference (about .018" usually) and take that much more off the head. Now you're up to .086", but since you probably started at less than 8:1 you're still under 9:1. You must measure the deck height and combustion chamber volume so you know where you are now and can determine what you need to do to get what you want. How much you can shave off the head without needing shorter pushrods depends on how much of the rocker adjusting screw is below the rocker body. |
|
| Author: | Charrlie_S [ Wed Jul 07, 2010 4:43 am ] |
| Post subject: | |
OP you need to measure, the bore, stroke, deck height, gasket thickness, and combustion chamber CC's. That will tell you the CR, you have now. From there it can be determined how much to cut the head/block, to get what you want. Also please sign up and log in. Please don't request tech help using the userhelp log in. If you are having trouble logging on, use the userhelp login, and post a help request in the "how to use this message board" section. Thanks |
|
| Author: | userhelp [ Thu Jul 08, 2010 12:29 am ] |
| Post subject: | |
I am signed in with a pass word. The site would not leet me sign in. The userhelp was the only way I could post. |
|
| Author: | Charrlie_S [ Thu Jul 08, 2010 4:39 am ] |
| Post subject: | |
Quote: I am signed in with a pass word. The site would not leet me sign in. The userhelp was the only way I could post.
Put a post in the "how to use this message board" forum, listing you user name, or send me a PM, and I will try to fix the problemhttp://www.slantsix.org/forum/viewforum.php?f=15 |
|
| Author: | Brussell [ Fri Jul 09, 2010 6:45 am ] |
| Post subject: | |
Hi, sorry I'm abit new to this. How come it wouldn't be 8.25:1? Guessing it's something to do with aging, or factory specs weren't 100% or some slants were different so they might have a different model? Or is there something else? Thanks |
|
| Author: | Joshie225 [ Fri Jul 09, 2010 8:08 am ] |
| Post subject: | |
Spec compression ratio is 8.4:1 for most slants. Production tolerances were such that most were below 8:1. The pistons are almost always lower in the cylinder than spec and the head volume is larger than spec. |
|
| Author: | Daddiojoe [ Mon Jul 12, 2010 10:41 am ] |
| Post subject: | |
The generally agreed upon number, and what I used to get the compression up to approx 9.5:1 is a whole .1" off of the head. Best of luck, Joe |
|
| Author: | Joshie225 [ Mon Jul 12, 2010 11:47 am ] |
| Post subject: | |
Sorry, but I disagree. You must measure the deck height and combustion chamber volume to determine how much to mill from the head to achieve a target compression ratio. .100" off my current head would not have gotten me 9:1 let alone 9.5:1. I had my head milled .080" which left it with 50cc combustion chambers. With a FelPro gasket on my untouched '67 225 I am at 8.5:1. |
|
| Author: | Greg Ondayko [ Mon Jul 12, 2010 4:25 pm ] |
| Post subject: | |
The head chambers and heights of the deck of the engine vary a bit. Greg |
|
| Page 1 of 1 | All times are UTC-08:00 |
| Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/ |
|